Sprinkle 1 teaspoon ground cinnamon on the pears and toss to coat.
2 teaspoons cinnamon
Transfer pears to an 8 or 9 inch square baking dish. Optionally, use a 10" cast iron skillet.
Combine the oats, brown sugar, butter, nuts, and remaining cinnamon in a mixing bowl. Use a pastry blender or sturdy fork to cut the butter into the dry ingredients until well blended.
1 cup rolled oats, 1 cup packed brown sugar, 1/2 cup butter, 1/2 cup nuts
Sprinkle the topping evenly over the prepared pear filling.
Bake at 375ºF for 35-40 minutes until edges are bubbly and topping is lightly browned.
Notes
If you'd like, you can process half the oats in a blender to create a coarse oat flour. This makes the crisp topping a little less chunky.
The pears will release juices as they cook. You can add a tablespoon of instant tapioca to the uncooked pears before adding the topping to help thicken the juice, but it's entirely optional.